Definition
An electrical switch in a retractable landing gear system that senses when the gear has reached its fully extended (down and locked) position and signals the gear motor or hydraulic pump to stop driving the gear further down.
Plain English
A switch that tells the system the wheels are all the way down, so it knows to stop lowering them.
Context Anchor
Seen in retractable landing gear systems, especially when studying gear position lights, warning systems, and electrical gear controls.
Derivation
“Limit” means an endpoint or boundary. In this term, it refers to the endpoint of landing gear travel in the down direction, where the switch is triggered.
Why Pilots Care
If a down limit switch fails or is out of adjustment, the gear motor may keep running after the gear is down (causing damage or a popped circuit breaker), or the gear-down indication may never illuminate even though the gear is actually locked. Knowing this helps pilots interpret abnormal gear indications correctly.
Intuition Check
Do not read “limit” here as a pilot-set restriction. It means the mechanical endpoint where the landing gear has finished moving down.
Example Sentence 1
When the down limit switch closes, the gear motor shuts off and the green gear-down light illuminates.
Example Sentence 2
The pilot knew the warning horn would stop once the down limit switches on each strut were triggered.